The Department of Homeland Security recently released immigration statistics through the end of 2010 for refugees and asylum seekers. It gives an overview of the major sources of international refugees for the U.S., which North Korea certainly is not. Instead, for the North, there is Table 14, an Excel spreadsheet listing all refugee arrivals by region and country from 2001 to 2010. Here, you can see the first nine NK refugees arrived in the U.S. in 2006, with 22 in 2007, 37 in 2008, before declining to 25 in 2009 and only 8 in 2010.
I’ll do some further research to try and determine the cause of the decline. For the sake of comparison, hundreds of thousands of North Korean refugees are thought to be in China, with another 20,000 defecting to the South since the Korean War.